The present disclosure relates to an exhaust diffuser and a gas turbine having the same and, more particularly, to an exhaust diffuser having an ejection hole and a suction hole, and a gas turbine having the exhaust diffuser.
In general, as shown in FIG. 1, a gas turbine 10 is composed of a compressor 15, a combustor 25, and a turbine 40. Air flowing inside through an air inlet 20 is compressed into high-temperature and high-pressure compressed air by the compressor 15. High-temperature and high-pressure combustion gas 35 (working fluid) is produced by combusting the compressed air by supplying fuel 30 to the compressed air in the combustor 25. The turbine 40 is operated by the combustion gas 35, and a power generator 50 connected to the compressor 15 is operated.
One important aerodynamic problem encountered during normal operation of a gas turbine engine 10 is to efficiently discharge combustion gas flowing out with high momentum through the last stage 60 of a turbine 40. It may be aerodynamically advantageous to configure a horizontal exhaust line, but axial exhaust may be substantially impossible due to influence on the entire footprint. For this reason, it is standard in the field to use vertical and side exhaust stacks that change the flow of combustion gas from an axial direction into the radial direction.
In detail, a radial diffuser may be used to guide combustion gas into the radial direction. As shown in FIG. 2, a radial diffuser 100′ generally includes a plurality of struts 140′ mounted on an internal diffuser guide 150′ and surrounded by an external diffuser guide 130′. The radial diffuser 100′ changes the kinetic energy of the combustion gas flowing out through the last stage of the turbine into potential energy of increased static pressure. Increasing the entire restoration of static pressure increases the performance and efficiency of the entire gas turbine engine. Accordingly, there has been an effort to develop an improved diffuser and an improved exhaust system to be used for gas turbine engines.
Several technologies for preventing flow separation by controlling the boundary layer of the flow at the inlet of a diffuser have been developed in correspondence to the above efforts. However, according to the technologies, it is very difficult to prevent flow separation between an internal diffuser guide and struts. Such flow separation causes a loss of pressure and consequently reduces the performance of the entire combustor. Therefore, there has been an effort to develop an exhaust diffuser that can solve the problems in the related art.